Extrusion process



Fe. 4, 1958 H. LORANT 2,822,687

EXTRUSION PROCESS Filed 001;. 21. 1953 2 Sheets-Sheet 2 v IN VEN TOR. 4 fie/a0 Z ORR/VT BY W ts mumw,

United States Patent EXTRUSION PROCESS Hugo Lorant, New York, N. Y.

Application October 21, 1953, Serial No. 387,465

1 Claim. (Cl. 207-) This invention relates to improvements in apparatus for plastically forming material, as by extrusion, and more particularly relates to improvements in metal extrusion presses of the type used in producing tubes from pre-heated solid billets which are pierced and extruded in one continuous operation.

Metal extrusion presses of the type to which the present invention relates employ a platen mounted in a relatively stationary position on the press bed, a billet container, and an extrusion tool operating ram, with the container being mounted between the platen and the ram and the platen having means for supporting a die at the side facing toward the billet container. The extrusion tool in presses of the described character includes a hollow extrusion stem extending from the ram in the direction toward the container to act against an annular dummy block in the container, through which a. piercing mandrel, slidable telescopically within the hollow stem, can be axially extended. In producing extruded tubes, a preheated billet is inserted in the bore of the liner carried by the billet container, with the billet usually having a diameter smaller than that of the liner bore to facilitate its insertion in the liner. Thus, the billet, when placed in the liner, rests on the bottom or one side of the latter, and an eccentric clearance exists between the internal surface of the liner and the billet. Before the billet is pierced, the billet should be upset or expanded radially to eliminate the eccentric clearance and completely fill the bore of the container liner. The failure to eliminate such eccentric clearance, prior to piercing of the billet, causes uneven flow of the metal to deflect the mandrel during piercing so that the pierced hole is not concentric with the surface of the billet and results in objectionable eccentricity or non-uniform wall thickness in the extruded tube, particularly at the front end thereof which is extruded first. Heretofore, efforts have been made to eliminate the eccentric clearance of the billet within the container liner prior to piercing of the billet by forcefully applying the dummy block against the adjacent end of the billet within the container before effecting the piercing stroke of the mandrel. However, in existing presses, the billet container is held against movement relative to the die during the stroke of the extrusion stem and the latter initially upsets the adjacent end of the heated billet to urge that end into frictional contact with the inner surface of the liner. Such frictional contact of the upset end of the billet with the liner prevents axial movement of the billet in the liner so that little or no upsetting pressure is transmitted to the end of the billet remote from the dummy block and an eccentric clearance continues to exist between that end remote from the dummy block and the inner surface of the liner to cause uneven flow during extrusion and the resultant eccentricity, particularly at the front end of the extruded tube.

Accordingly, it is an object of the present invention to provide a metal extrusion press of the described character for producing extruded tubes which is constructed and operated in a manner effecting complete upsetting of the 2,822,087 Patented Feb. 4, 1958 billet to fill the liner of the billet container prior to the piercing operation and thereby to avoid objectionable eccentricity of the extruded tube.

More specifically, it is an object of the present invention to provide a metal extrusion press for producing extruded tubes by direct extrusion, that is, by movement of the extrusion tool relative to the billet container and die (as distinguished from indirect extrusion in which the billet container, with the billet therein, is moved relative to the die), and wherein, prior to piercing of the billet by the piercing mandrel, the billet is upset along its entire length to completely fill the bore of the container liner and avoid objectionable eccentricity of the pierced hole and extruded tube.

The present invention provides an extrusion press of the described character for producing extruded tubes in which the billet container is movable toward the platen while being opposed by a predetermined resistance during the application of pressure by the extrusion stem through the dummy block against the adjacent end of a heated billet in the container so that, when that adjacent end of the billet is upset and urged into frictional contact with the inner surface of the container liner and that frictional contact becomes suflicient to present a frictional resistance to movement of the billet relative to the container which is greater than the above mentioned resistance to movement of the billet container toward the platen, the billet container is then displaced toward the platen by continued advancement of the ram with the die entering the liner of the billet container to upset the end of the billet remote from the dummy block and thereby completing the elimination of the eccentric clearance between the billet and liner.

The invention will be more readily understood by consideration of the accompanying drawings which illustrate an embodiment of the invention merely by way of example.

In the drawings:

Fig. 1 is a longitudinal vertical section of a metal extrusion press embodying the apparatus of the present invention;

Fig. 2 is a fragmentary, transverse sectional view of a billet placed in the liner of the billet container of the press of Fig. l, and taken along the line 22 of Fig. 3;

Fig. 3 is a fragmentary, longitudinal sectional view of a portion of the press of Fig. 1 shown on an enlarged scale at the beginning of the billet upsetting operation;

Fig. 4 is a view similar to Fig. 3, but at the conclusion of the initial phase of the billet upsetting operation;

Fig. 5 is a view similar to Figs. 3 and 4, but at the conclusion of the billet upsetting operation; and

Fig. 6 schematically illustrates a system for supplying pressurized fluid to cylinders included in the press of Fig. 1.

Referring to the drawings in detail, and initially to Fig. 1 thereof, a metal extrusion press embodying the present invention is there generally identified by the reference numeral 10. The press 10 is generally of a conventional type for extruding metal tubes wherein the bed extends horizontally and the motion of the tools and of the "billet container is in a horizontal direction. It is to be understood, however, that the invention may be applied to various other types of apparatus for plastically forming material into tubes by direct extrusion, that is, by movement of the tools relative to the billet container and die, such as, for example, to metal extrusion presses of the vertical type.

The extrusion press 10 shown in the drawings has a horizontal bed 12 provided with a cross-head 14 at one end which supports the main power cylinder 16 for effecting movement of the extrusion tools. A platen and die supporting structure 18 is mounted at the end of bed 12 3 l remote from the cross-head 14, and cross-head 14 and structure 18, at the opposite ends of the bed, are connected together, as shown, by parallel, longitudinally extending tie rods 20.

The main power cylinder 16 is provided with the customary fluid inlet and outlet (not shown), and a piston or ram 22 reciproeable in cylinder 16 has a movable cross-head 24 connected .t'oits free or outer end for sliding movement along the bed 12. A hollow extrusion stem 26 extends from movable cross-head 24, and a piercing mandrel 30 is telescopically slidable within the extrusion stem 26 for movement relative to the latter from a position withdrawn within the extrusion stem to an extended position in which it may project through the .dummy block 28 which is in the container at the billet. An auxiliary piston rod or ram 32 is connected to the piereingrnandrel and is reciprocably received in an auxiliary power cylinder 34 having the customary fluid inlet and outlet (not shown) for effecting the movements of the piercing mandrel relative to the extrusion stem and dummy block. The power thrust of ram 22 is toward the left, as viewed in Fig. 1, and is effected by the action of pressurized, preferably hydraulic, fluid in the main power cylinder 16, while the head 24 is returned to the right by suitable pull back motors (not shown) which have their piston rods connected to the cross-head 24 in the customary manner.

The platen structure 18 fixed to bed 12 .has a central opening 36 therethrough for receiving the extruded tube and, at its side facing toward the movable cross-head 24, the platen structure carries a die support arrangement, indicated generally by reference numeral 38, for supporting an extrusion die 40 in axial alignment with the extrusion stem 26, the bore through the billet container, and the opening 36 of the platen.

The billet container housing '42, disposed between the fixed platen structure and the tool carrying ram 22, supports the billet container composed of a main body portion 44 and a renewable liner 46 having an axial bore extending therethrough to receive the heated billet to be extruded. The container housing 42 is provided with suitable guide shoes (not shown) which ride on corresponding guide surfaces provided on the tie rods v20 so that the container housing, and with it the body portion 44 and liner 46 of the billet container, are movable toward and away from the fixed platen structure 18. As seen in Figs. 1, 3, 4 and 5, the die 40 is dimensioned to extend into the adjacent end of the bore of liner 46 when the billet container is moved toward the platen structure, and the die support 38 is arranged to expose a substantial axial portion of the die for such extension into the liner of the billet container.

In accordance with the present invention, 'a predetermined resistance is provided to movement of the billet container toward the fixed platen structure from 'aposition (Figs. 1, 3 and 4) in which the liner 46 is spaced axially from an abutment face 48 of aportion of the die support 38 holding the die 40 with the outer part of the die being introduced into the bore of liner46. Such predetermined resistance to movement of the billet container from the above defined position may be provided by friction, or may be provided by hydraulic'container moving cylinder means 50 (Fig. 1) which are supported inthe fixedplaten structure 18 with their axes extending parallel to the direction of movement of the billet container and have piston rods 52 extending therefrom. The rods 52 have threaded end portions, as shown, extended through the billet container housing '42 and secured to the latter by nuts at the opposite sides of the housing. Fluid is supplied to the cylinders 50 from a suitable source, such as an accumulator 59, and the pressure of the fluid in the left ends of the cylinders (Fig. l) 50 provides-a yieldable and predeterminable resistance to movement of the billet container toward the platen structure, with the magnitude of this resistance being dependent upon the pressure of the fluid supplied to the left ends of cylinders 50 and the piston areas within the latter against which the pressure fluid is free to work. Control box 58 (Fig. 6) can be used to control fluid pressure applied to the ends of cylinder means 50 so as to govern the position of the container and the pressure in the left ends of the cylinders 50 when the extrusion stem is being operated. For example, a pressure regulating or relief valve can be inserted in the feed line to the left ends of cylinders 50.

In employing a press of the described character for the extrusion of tubes from a heated metal billet, a billet is first placed in the bore of liner 46 of the billet container and, as shown in Fig. 2, the diameter of the billet 54 is usually smaller than the internal diameter of liner 46 to facilitate the placement of the billet in the container. The dummy block 28 then may be inserted into the container. When the billet 54 rests upon the bottom of the liner, an eccentric clearance 56 is left between the surface of the billet and the internal surface of the liner. If an attempt was made -to pass the mandrel 30 through the billet 54 while the eccentric clearance 56 existed, the transverse flow of the metal would be uneven, by reason of the non-uniform resistance to such flow resulting from the eccentric clearance, and such uneven transverse flow of the metal would cause deflection of the mandrel so that the hole pierced through the billet would be eccentrically located to cause corresponding excessive eccentricity in the .tube extruded from the pierced billet. In the conventional arrangement, it is not possible to eliminate the eccentric clearance 56, prior to piercing of the billet, by applying pressure through the dummy block 28 against the adjacent end of the billet54 in the liner 46 to axially compress the billet and thereby to upset or effect radial expansion of the billet until it fills the bore of the container liner. In existing presses, the upsetting of the billet is carried out with the billet container in a fixed position relative-to the platen-structure and the die carried by the latter, and with the axial pressure through the dummy block against'the adjacent end of the billet causing initial axial compressionand corresponding radial expansion of that'adjacent end of the :billet into frictional contact with the internal surface of the container liner. Axial compression and radial expansion of the billet at the end remote from the dummy block could be achieved with a fixed container only if 'the initially uspet end of the billet would be free to shift axially within the liner to transmit the upsetting pressure of the extrusion stem 26 through the dummy block to the end of the billet adjacent'the die; however, the frictional contact between the initially upset end of the billet and the liner will resist such axial shifting of the billet within the liner of the positionally fixed container and an excessive pressure would have to be applied by the stem 26 to overcome the resistance of such frictional contact, particularly since the pre-hea'ted metal forming the billet is chilled by contact with the container and the dummy block and die. Further, the application of excessive pressure axially against the billet would result in the commencement of extrusion through the die opening rather than axial compacting of the billetto fill the bore of the liner.

In accordance with the present invention, the billet container is initially positioned as shown in Fig. 3 with the end of liner 46 being spaced from the face 48 of the die supporting structure 38 and with the die 40 extending into the bore of liner 46 to engage the adjacent face of the billet 54. Fluid is fed to main power cylinder 16 to advance cross-head 24 and stem 26, with the end of piercing mandrel 30 being flush with the outer face of dummy block 28 as it acts against the billet. As force is exerted axially against the adjacent end of billet 54 (Fig. 4), that end is upset and expanded radially to fill the related portion of the bore of liner 46, while axial shifting of the liner-and the main body '44 and holder 42 .of the billetcontainer is resisted by pressure fluid supplied to the cylinders 50 adjacent control box 58. However, as

the end of billet 54 acted on through the block 28 expands into frictional contact with the internal surface of liner 46 the axial force exerted against the billet 54 through the dummy block is transmitted by such frictional contact to the liner 46, and hence to the body 44 and holder 42 of the billet container, and overcomes the resistance offered by the fluid pressure in the left ends of cylinders 50 so that the billet container shifts axially toward the platen structure 18 until the surface 48 is abutted against by the adjacent end of liner 46 (Fig. 5). During such axial shifting of the billet container, the liner 46 moves further over the die 40 so that the latter acts against the adjacent end of the billet 54 to upset and radially expand the last mentioned end until the bore of liner 46 is circumferentially filled by the billet along the entire length of the latter, as shown in Fig. 5. A slight deformation of the billet may take place at the die opening, and a modicum thereof may enter the die opening in the form of a small protruding nipple (not shown), or the like.

When the billet has been fully upset in the manner described above, power cylinder 34 is energized to advance the piercing mandrel 30 relative to the extrusion stem 26, and the mandrel 30 is thereby projected through the block 28 and pierces the billet. Since the billet fills the bore of liner 46, flow of metal during the piercing operation is uniform in all directions and there is no tendency to laterally deflect the piercing mandrel thereby ensuring that the pierced hole formed in the billet is concentric with respect to the die opening and the bore of the liner. After the billet has been pierced, the extrusion stem is further advanced into the billet container to extrude the metal of the billet through the die opening around the concentric mandrel thereby extruding a tube of practically uniform wall thickness, including the front end of the tube which is extruded from the portion of the billet adjacent die 40.

Referring to Fig. 6, pressure may be supplied to cylinders 50 through pipe 64, 64a and 64b from the accumulator 59. As previously mentioned, control 58 of any suitable type can be used to supply fluid to the appropriate ends of cylinders 50.

While a particular embodiment of the invention has been described in detail and illustrated in the accompanying drawings, it is to be understood that the particular embodiment is merely exemplary and the invention is not limited thereto, and that various changes and modifications may be efiect'ed therein without departing from the scope of the invention as defined by the claim appended hereto.

What is claimed is:

The process of forming tubular shapes by extruding metal from a solid billet in an extrusion press having a billet container and die movable relative to each other, said container having a bore and said die having an extending portion movable into said bore, comprising the steps of spacing said container from said die with at least part of said extending portion outside of said bore, placing a solid billet in said bore, compacting said billet in said bore by exerting force on the end of said billet furthest from said die, yieldably resisting the movement of said container toward said die and holding the container in its spaced position until suflicient force is transmitted to said container by frictional contact between the container and the billet to overcome said resistance and move said container relative to said die and said extending portion so as to completely upset said billet to eliminate radial clearance throughout its length, positively stopping the billet container at the end of the upsetting operation with the bore completely overlying the extending portion, piercing said billet, and thereafter extruding said billet through said die.

References Cited in the file of this patent UNITED STATES PATENTS 1,574,792 Clark Mar. 2, 1926 2,128,705 Hatebur Aug. 30, 1938 2,337,804 Dempsey Dec. 28, 1943 2,491,897 Lorant Dec. 20, 1949 2,675,125 Genders Apr. 13, 1954 FOREIGN PATENTS 14,330A Great Britain June 29, 1896 459,020 Great Britain Dec. 31, 1936 

